This invention relates generally to hydraulic circuits, and more particularly to a hydraulic circuit for a bottom dump front shovel which offers more rapid apron closing and repositioning of the bucket to the digging position.
Hydraulic circuits incorporating interrupted series control valves have long been used in various fields, and particularly in construction equipment such as excavators and front loaders and the like. One disadvantage of any circuit utilizing interrupted series control valves is that only one valve in the bank of valves can be operated at one time. Thus, if the first valve is actuated, that valve controls the flow of the hydraulic fluid. As an example, in an excavator, the first circuit may control the bucket movement and the second circuit would control the apron movement. Then in the present circuitry, there could not be simultaneous apron and bucket movement without auxiliary pumps, valves, conduits, etc.
In an excavator, for example, it is desirable for the operator to return the bucket to its digging position as quickly as possible in order to cut down on the cycle time. In the above-described circuitry, simultaneous return of the bucket and closing of the apron was not possible under full speed conditions due to the interrupted series control valves. It is, of course, possible to operate both circuit control valves simultaneously in the fine modulating mode. However, this is not satisfactory from the speed standpoint.
Accordingly, it is an object of this invention to provide a hydraulic circuit which offers more rapid apron closing and repositioning of the bucket to the digging position.
Another object of this invention is to provide a hydraulic circuit which will permit diverting a portion of the flow from the first circuit to perform the end function of the second circuit, thereby offering simultaneous operation of both circuits under maximum speed operational conditions.
A further object of this invention is to provide a hydraulic circuit which will permit an operator to return the bucket and close the apron simultaneously in order to reduce the cycle time from dump to dig.
And yet another object of this invention is to provide a hydraulic circuit which will permit independent operation of either circuit through the interrupted series control valves.